The present invention generally relates to electron emitter materials and more specifically provides a new class of electron emitter devices based on carbon nitride.
Carbon nitride (CN) has been investigated due to its potential as an industrial material due to a number of predicted desirable properties, including hardness. Carbon nitride exists in several crystalline structures. The structure of a carbon nitride film may run from amorphous to polycrystalline to single crystal.
In U.S. Pat. No. 5,405,515, xe2x80x9cMETHOD AND APPARATUS FOR PRODUCTION OF A CARBON NITRIDE FILM,xe2x80x9d a method of forming carbon nitride films based on a combination of a carbon arc and a nitrogen plasma is disclosed. The material is described as useful in applications where superior surface hardness is required.
In U.S. Pat. No. 5,110,679, crystalline carbon nitride films are disclosed which are fabricated by sputtering from a carbonaceous target in the presence of a nitrogen atmosphere onto a single crystal silicon or germanium substrate. It is disclosed that carbon nitride may be used as a high temperature structural material with good strength-to-weight ratios.
Cathodes are used in a number of electronic devices such as displays, power amplifiers and vacuum microelectronics. Conventional cathode structures are relatively low current devices which require either high extraction voltages or elevated temperatures for operation. Accordingly, it would be desirable to provide a cold cathode which would function at lower temperatures and voltages than existing cathodes.
It is an object of the present invention to provide a cold cathode material which is capable of producing large currents at relatively low applied fields and at nominally ambient temperature.
It is another object of the present invention to provide microelectronic devices having a cathode structure fabricated of carbon nitride.
It is yet another object of the present invention to provide such cold cathode materials which can be fabricated by reactive laser ablation, chemical vapor deposition or sputtering processes.
In accordance with the present invention, a cold cathode material is provided which comprises carbon nitride. The carbon nitride cold cathodes of the invention may be amorphous carbon nitride, polycrystalline carbon nitride or single crystal carbon nitride. The cold cathodes of the present invention may comprise mixed forms of the various phases of carbon nitride. The carbon nitride cold cathodes of the invention may be operated at temperatures as low as 20xc2x0 C. with extraction voltages of as low as 10xe2x88x922 volts/xcexcm. They are capable of producing currents as high as 100 amperes/cm2.
In another aspect the present invention provides a new class of electronic devices in which the cathode material is carbon nitride. These devices include lamps, flat panel displays, power amplifiers, vacuum microelectronics, radiation hard computers and transient suppression devices and the like.
In still another aspect, the cold cathodes of the invention are composite structures of carbon nitride, boron nitride and diamond. A diamond layer is created by microwave or some other type of CVD which serves as a substrate on which a thin boron nitride layer is deposited. A carbon nitride layer is then formed on the boron nitride layer. The boron nitride layer and the diamond layer are doped n-type.
In still another aspect the cold cathodes of the invention are free-standing structures of carbon nitride.
In still another aspect the invention provides methods for fabricating carbon nitride cold cathodes by laser ablation deposition utilizing a reactive biased laser ablation technique in which the surface of a silicon substrate is first pretreated with atomic hydrogen and then irradiated with a laser plume energized by at least one biased ring. A doped cubic boron nitride layer is preferably first deposited under biased conditions in an argon/nitrogen, dopant/nitrogen/argon or dopant/nitrogen atmosphere. A carbon nitride layer is then formed on the boron nitride layer under biased conditions in a nitrogen/argon or nitrogen, argon, carbon-bearing gas (CH4 etc.) atmosphere. The carbon nitride surface layer is then annealed with an atomic hydrogen plasma.
In still another embodiment the carbon nitride cold cathodes of the invention are formed using a reactive sputtering process. Sputtering is carried out by magnetron sputtering deposition using a carbon target in a nitrogen or nitrogen argon, or nitrogen, argon, carbon-bearing gas (CH4 etc.) atmosphere.
Other objects, features and advantages of the present invention will become apparent upon consideration of the specification and the appended drawings.